1. Field of the Invention
The present invention relates to various means for housing and protecting microelectronic circuitry in order to prevent external access to sensitive data stored therein.
2. Description of the Prior Art
Several known prior art techniques have been proposed for providing a housing for microelectronic circuitry.
British Patent Specification No. 1,245,710 discloses a case containing a semiconductor integrated element. The case is comprised of a bottom plate, a middle plate and an upper or sealing plate. The integrated element is disposed in a recess in the bottom plate, which bottom plate is comprised of a plurality of ceramic sheets having preselected conductive leads and conducting layers selectively provided thereon. Connections between the paths on the ceramic sheets are selectively made by way of preselected perforated holes through the sheets to the conducting layers and conducting leads. The middle plate is fixed between the bottom plate and the upper or sealing plate to complete the enclosure of the semiconductor integrated elements. The conductive leads are fed out of the case for external connections.
British Patent Specification No. 2,077,036A discloses a multi-layer ceramic package comprised of multi-layers of ceramic substrate on which conductive patterns are selectively placed. The conductive patterns on the various ceramic layers are selectively connected to each other by plated through holes or tunnels. An array of chips, bonded on one of the ceramic substrates, is interconnected by way of wire bondings through lands disposed between and separating the chips.
Neither of the two above-identified British Patent Specification Nos. 1,245,710 and 2,077,036A provides any protection from the unauthorized access of sensitive data that may be stored in the microelectronics circuitry located in its associated housing. To solve this problem, the following known prior art techniques have been proposed.
Ericsson, a company located in Sweden, has proposed a security module to physically protect electronic components, and information stored in such electronic components, from unauthorized analysis and manipulation by physically encapsulating such electronic components. These encapsulated blocks are called Ericsson SEC modules. Ericsson states that such SEC modules effectively protect algorithm sequences, semi-processed data and algorithm keys used in PIN (personal identification number) verification by storing certain information in a volatile RAM (random access memory). Ericsson further states that the encapsulation of the SEC module and a key pad is designed in such a way that it is impossible, even by a combination of chemical and physical attacks, to gain access to the secret data (i.e., algorithm keys) stored in the volatile RAM because this information would be destroyed if the SEC module were attacked.
Further information on the SEC module and how such protection of the secret data is achieved is unavailable to the applicant of the instant invention, since Ericsson has internally classified the design drawings and documentation for the sensitive parts of the SEC module and has only allowed authorized persons to have access to such information.
PCT Application No. WO84/04614 discloses a data security device which includes a closed prestressed glass container within which are a data processor and a volatile memory for storing encryption key data. A power supply for the memory is connected to the memory by way of one or more conductors which wind over the entire inside surface of the closed container. As a result, a breaking into the closed container will break a conductor, removing power from the memory and thereby destroying the data stored in the memory.
German Offenlegungsschrift No. 3,023,427 discloses a secure mobile data storage unit which includes solid state electronic memories contained within a tamperproof housing and pressure difference sensors built into the housing to detect any unauthorized entry into the housing and to initiate the erasure of data stored in the memories after such detection.
The background art known to applicant at the time of the filing of this application is as follows:
British Patent Specification No. 1,245,710, Case For Containing A Semiconductor Element;
British Patent Specification No. 2,077,036A, Multi-Layer Ceramic Package For Semiconductor Chip;
A publication on the Ericsson SEC module;
PCT Application No. W084/04614, Data Security Device; and
German Offenlegungsschrift No. 3,023,427, Mobile Data Storage Unit.